1. Field of the Invention
The present invention relates to the field of gene therapy. According to the present invention, methods are provided for the treatment of functional spinal unit injuries through the use of light activated gene therapy to introduce a desired gene into a patient's tissue. An embodiment of the present invention includes methods for the utilization of light activated gene therapy to repair/rebuild an injured intervertebral disc. Alternate embodiment provide an implant system having UV activated viral vector integrated with an implant.
2. Description of the Related Art
Currently, treatment for injured spines often involves “fusion” or inciting the biological union of bones by inserting bone grafts or devices within the functional spinal units (FSU), e.g., between two vertebra. In addition, the effective manipulation of certain osteobiologic molecules via gene therapy can be used to incite bone fusion within a functional spinal unit (FSU). A FSU is composed of two vertebra, a nearby nerve root, and a human interverterbral disc between the two vertebra. This disc, which cushions shock to the spine and lends stability to the FSU, is composed of water, collagen (Type I and II), and glycosaminoglycans (GAG).
An aging or degenerate disc is often characterized by reduced water, increased Type I collagen, decreased Type II collagen, and decreased GAG. This aging or degenerating, which is incompletely understood, generally results in decreased biomechanical shock absorption, increased range of motion and pain and/or disability.
Somatic cell gene therapy is a form of treatment in which the genetic material of a target cell is altered through the administration of nucleic acid, typically in the form of DNA. In pursuit of effective in vivo administration routes, scientists have harnessed the otherwise potentially deleterious ability of viruses to invade a target cell and “reprogram” the cell through the insertion of viral DNA. By encapsulating desirable genetic material in a viral particle, or “vector,” minus some of the viral DNA, the effective and targeted delivery of genetic material in vivo is possible. As applied to spinal specific treatments, gene therapy offers the ability to make use of osteobiological molecules, including both intracellular and extracellular proteins, to incite bone fusion and/or disc repair.
In particular, the desirable qualities of adeno-associated viruses (AAV) have led to further study of potential gene therapy uses. As a vehicle for gene therapy recombinant forms of AAV, or r-AAV, offer many advantages including the vector's ability to infect non-dividing cells (e.g., chondrocytes, or cells within cartilage), the sustained target gene expression, the low immune response to the vector, and the ability to transduce a large variety of tissues. The AAV contains a single strand DNA (ssDNA) genome. Under normal conditions, AAV is present in humans in a replication incompetent form, due to the fact the AAV alone does not encode the enzyme required for replication of the second DNA strand. Successful r-AAV transduction often requires the presence of a co-infection with an adenovirus or the exposure of the host cell to DNA damaging agents, such as γ-irradiation. The introduction of either the co-infection or the DNA damaging agents dramatically induces the rate limiting step of second strand synthesis, i.e. the second strand of DNA which is synthesized based on the vector inserted first strand. However, making use of these DNA damaging agents is impractical because the administration of an adenovirus co-infection to a patient is not practical or desirable and the site specific and safety issues involved with using γ-irradiation are undesirable as well.
In the past, attempts have been made to induce r-AAV transduction in vitro using UV radiation having a wavelength of 254 nm. Unfortunately, no effective therapeutic method or apparatus was developed based on these experiments due to the long exposure times involved with using 254 nm UV radiation, the difficulties of delivering 254 nm UV radiation to a surgical target site, and the inability to position the 254 nm UV light source so as to allow effective penetration of a target cell.